Wednesday, February 18, 2009

Wrapping up Chapter 22...

Well my fellow classmates of Biology in B and C block, here's the agenda for tonight's blog:
Let's finish up the chapter 22 notes and then study a little for our 22 quiz, shall we?

CHAPTER 22: Descent with Modification: A Darwinian Way of Life CONTINUED

-Homology: related species share characteristics; but this does NOT necessarily mean these characteristics share t
he same function.
-Homologous Structures are anatomical signs of evolution. If you look at the forelimbs of humans, cats, whales, and bats, they are all made of basically the same bones. Therefore, they all share a common ancestry. However, they use these limbs for all different things: lifting, walking, swimming, and flying.
-some homologous structures can only be seen in the embryo form of organisms. For example, ALL vertebrate embryos (including humans) have a tail behind the anus... these are called embryological homologies
-another type of homology are molecular homologies: occurring when organisms share characteristics on the molecular level (ex: use the same method for reproducing DNA or other cellular processes)
-some structures passed down from ancestors are no longer used by the present species-- these are vestigial structures
-vestigial structures can be great clues to tracking down the ancestry of a given organism. for example, some snake skeletons contain remnants of the pelvis and leg bones of their walking ancestors
-animals sharing a common ancestor may develop homologies that their ancestors did not have. for example, all tetrapods today have the same limb bone structure, but their ancestors do not.
-evolutionary tree: used to represent the pattern of descent from common ancestors and the resulting homologies

-Convergent Evolution: organisms evolve independently from different ancestors, but they adapt to similar environments in similar ways. They, therefore, share features that are analogous: they serve the same purpose.
-biogeography, the geographic distribution of species, also results in evolution. As continents drift apart it isolates populations often resulting in new species through adaptation and genetic drift. (a species only found in a certain area is called an endemic species-- these species are more prone to extinction)
-Linnaeus, known as the father of taxonomy, the naming and classifying of organisms, developed the system of binomial nomenclature still used today. He adopted a system for grouping species into categories and ranking the categories into a hierarchy.

Alrighty folks, that seems to be the end of Chapter 22. C Block didn't make it to any notes on 23, so that's all I've got. Here's a short review to help with the Chapter 22 Quiz manana:

1. If structures on several organisms share basic function but not ancestry, are they homologous or analogous?
2. According to Charles Darwin's theories on evolution, what is the result of natural selection?
3. __________ is the study of fossils.
4. Was Lamark's theory on evolution (characteristics acquired during an organisms lifetime can be passed on to the next generation) proved correct or incorrect?
5. Homologies that are not usually seen during adulthood are called ________ ________.

1. analogous
2. the adaptation of a population to its environment
3. Paleontology
4. incorrect
5. embryonic homologies

Night night everyone. Good luck tomorrow.

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